1. Field of the Invention
The present invention relates to a manufacturing method of a semiconductor device, in which a barrier insulating film and a main insulating film having low relative dielectric constant are sequentially formed to coat a wiring consisting mainly of copper film.
2. Description of the Prior Art
In recent years, a higher data transfer speed has been required in addition to higher integration of a semiconductor integrated circuit device. For this reason, it has been provided with an insulating film having low relative dielectric constant and thereby small R-C delay (hereinafter, referred to as a low relative dielectric constant insulating film).
In order to form such a low relative dielectric constant insulating film, there is known a plasma enhanced CVD method using trimethylsilane (SiH(CH3)3) and N2O. For example, the method is described in Electrochem. Soc. Fall Meeting Abstacts, p.344(1998) by M. J. Loboda, J. A. Seifferly, R. F. Schneider, and C. M. Grove, or the like. Further, a plasma enhanced CVD method using tetramethylsilane (Si(CH3)4) and N2O is described in SEMICON Korea Technical Symposium 2000, p.279(2000), or the like by J. Shi, M. A -Plano, T. Mountsier, and S. Nag, for example.
There is known a plasma enhanced CVD method using phenylsilane or the like as another method. It is described in The 46th Spring meeting of The Japan Society of Applied Physics (1999), p.897 by Kazuhiko Endo, Keisuke Shinoda, and Toru Tatsumi, The 60th Autumn meeting of The Japan Society of Applied Physics(1999), 1p-AN-9(1999) by Nobuo Matsushita, Yoshinori Morisada, Yuichi Naito, and Karyo Matsuno, The 4th Spring meeting of The Japan Society of Applied Physics (1999), p.897(1999) by Yukinori Uchida, Tsuneo Matsuzawa, Satoshi Kanno, and Masakiyo Matsumura, or the like.
When such insulating films with low relative dielectric constant are formed on the wiring consisting mainly of copper film, the barrier insulating film made of nitride film is firstly formed on the wiring consisting mainly of copper film to prevent copper from diffusing, and the insulating film with low relative dielectric constant is formed on the barrier insulating film.
In this case, when forming the barrier insulating film made of nitride film and the main insulating film having low relative dielectric constant are formed on the wiring consisting mainly of copper film by the CVD method, the nitride film is formed by nitrogen-containing gas first, and the gas is then switched to silicon-containing gas to form the insulating film having low relative dielectric constant. Gas flow rate or the like as well is appropriately adjusted along with switching of film forming gas. As described above, when the barrier insulating film and the main insulating film are sequentially formed on the wiring consisting mainly of copper film, there is a need for switching operation of gas, adjusting operation of the gas flow rate, and the like. Moreover, since much time is required to substitute the film forming gas inside a chamber after switching of gas, throughput is not improved.
The object of the present invention is to provide a manufacturing method of a semiconductor device, which is capable of forming the barrier insulating film having sufficient ability for preventing diffusion of copper and the main insulating film having sufficiently low relative dielectric constant while improving throughput, when the barrier insulating film and the main insulating film thereon are sequentially formed on the wiring consisting mainly of copper film.
Incidentally, when the film forming gas including silicon-containing gas and oxygen-containing gas is transformed into plasma by an electric power having low frequency of 1 MHz or less, 380 kHz for example, to cause reaction to form a film, and thus a dense insulating film can be formed. Accordingly, diffusion of copper can be prevented. Further, when the film forming gas is transformed into plasma by the electric power having high frequency of 1 MHz or more, 13.56 MHz for example, to cause reaction to form a film, the main insulating film having low relative dielectric constant can be formed. This is due to the reason as follows. Ions and the like are easily accelerated due to a large cathode drop voltage in the low frequency, and the film is densely formed by a so-called bombardment effect. On the other hand, the so-called bombardment effect is small in the high frequency since the cathode drop voltage is small. Thus, the film has low relative dielectric constant although denseness is lower comparing to that of the low frequency. In those events, the insulating films having the foregoing different capabilities can be formed while the same film forming gas is used in deposition.
In the present invention, substantially same gases which respectively contain the silicon-containing gas and the oxygen containing gas are used as the first and second film forming gases to form the barrier insulating film and the main insulating film having low relative dielectric constant. Specifically, the electric power having a first frequency f1 is applied to the first film forming gas to transform it into plasma, and the barrier insulating film is thus formed. And, the electric power having a second frequency f2 higher than the first frequency f1 is applied to the second film forming gas to transform it into plasma, and the main insulating film having low relative dielectric constant is thus formed. For example, the first frequency f1 is set to the frequency of 100 kHz or more and 1 MHz or less, and the second frequency f2 is set to the frequency of 1 MHz or more.
Therefore, multi-layer insulating films which have ability required for an inter wiring layer insulating film can be continuously formed on the wiring or the like mainly consisting of copper film by using the substantially same gases as the first and second film forming gases and only adjusting the frequency of the electric power for transforming the film forming gas into plasma. Accordingly, improvement of throughput can be achieved.
Any one of combinations of alkyl compound having siloxane bond with N2O, H2O or CO2 can be used as a preferable combination of the silicon-containing gas and the oxygen-containing gas.
Furthermore, if gas in which any one of nitrogen-containing gases such as ammonia (NH3) and nitrogen (N2) in particular is added to the silicon-containing gas and the oxygen-containing gas is used as the first film forming gas for forming the barrier insulating film, barrier ability against copper can be improved for a deposited insulating film. Moreover, if gas in which any one of methylcyclohexane (CH3C6H11) and cyclohexane (C6H12) in particular is added to the silicon-containing gas and the oxygen-containing gas is used as the second film forming gas for forming the main insulating film, lower relative dielectric constant can be achieved for a deposited insulating film.
Alternatively, using inert gas such as helium (He), argon (Ar) or nitrogen (N2) can dilute the film forming gas without resulting in spoiling adhesion between the wiring consisting mainly of copper film and the barrier insulating film.